This invention relates to targets for implosion by an energy source, and more particularly to a fusion target compatible with ion beam implosion techniques.
In recent years much effort has been directed to inertial confinement fusion involving the development of implosion apparatus and targets for implosion by energy sources, such as lasers and electron beam machines. More recently, development efforts have been directed toward ion beam implosion of fusion targets, thus establishing a need for targets compatible with ion beam technology.
While development efforts in the field of magnetic confinement have been carried on for at least two decades to develop a fusion power reactor, inertial confinement fusion (implosion of a fusion target be an energy source) efforts are relatively recent. For example, U.S. Pat. No. 3,378,446 to J. R. B. Whittlesey represents an early effort in inertial confinement to develop apparatus using lasers to trigger thermonuclear reactions whereby laboratory testing of fusionable materials in small quantity could be carried out. U.S. Pat. No. 3,489,645 issued Jan. 13, 1970 to J. W. Daiber et al is directed to a method of creating a controlled nuclear fusion reaction by repeatably imploding fusion targets by laser energy within an explosion chamber. U.S. Pat. No. 3,624,239 issued Nov. 30, 1971 to A. P. Fraas is directed to a pulsed laserignited thermonuclear reactor in which a fusion fuel target is imploded by a laser within a void in liquid lithium contained within a pressure vessel. U.S. Pat. No. 3,723,246 issued Mar. 27, 1973 to M. J. Lubin is directed to a plasma production apparatus having target production means and laser implosion means. U.S. Pat. No. 3,762,992 issued Oct. 2, 1973 to J. C. Hedstrom involved a DT target imploded by a laser wherein the neutron energy is dissipated in a lithium blanket to produce tritium, with the heat transferred to a thermodynamic plant as known in the art. U.S. Pat. No. 3,899,681 issued Aug. 12, 1975 to E. H. Beckner et al teaches an electron beam device for imploding hollow targets. In addition, various papers have been presented in this field as exemplified by "Fusion Power By Laser Implosion" by J. L. Emmett et al, Scientific American, June 1974; "Laser-Induced Thermonuclear Burn" by J. Nuckolls et al, Physics Today, August 1973; and "Laser Compression of Matter to Super-High Densities: Thermonuclear (CTR) Applications" by J. Nuckolls et al, Nature, Vol, 239, No. 5368, pp. 139-142, Sept. 15, 1972.
Also substantial effort has been directed to various components of the implosion system as evidenced by U.S. Pat. No. 3,723,703 issued Mar. 27, 1973 to K. W. Ehlers et al directed to a laser alignment and firing system for creating and heating a plasma by imploding targets; U.S. Pat. No. 4,017,163 issued Apr. 12, 1977 to A. J. Glass directed to angle amplifying optics for directing laser energy onto a target located within an explosion chamber; and U.S. Pat. No. 3,892,970 issued July 1, 1975 to J. R. Freeman et al directed to a realivistic electron beam device for producing a plasma therein; and a paper "Laser Fusion Target Illumination System" by C. E. Thomas, Applied Optics, Vol. 14, No. 6, June 1975.
Various target designs have been proposed for laser, electron beam, and ion beam implosion techniques as exemplified by "A 1964 Computer Run On A Laser-Imploded Capsule" by R. E. Kidder, UCID-17297 dated Mar. 25, 1973; "Implosion, Stability, And Burn Of Multishell Fusion Targets" by G. S. Fraley et al presented at The Fifth I.A.E.A. Conference on Plasma Physics and Controlled Nuclear Fusion Research, Tokyo, Japan, Nov. 11-15, 1974 as Paper IAEA-CN-33/F55 (LAUR-5783-MS); "Structured Fusion Target Designs" by R. C. Kirkpatrick et al, Nuclear Fusion 15, April 1975, pp. 333-335; "Target Compression With One Beam" by G. H. McCall et al, Laser Focus, December 1974, pp. 40-43; "Electrically Imploded Cylindrical Fusion Targets" by W. S. Varnum, Nuclear Fusion 15, December 1975, pp. 1183-1184; "The Calculated Performance Of Structured Laser Fusion Pellets" by R. J. Mason, Nuclear Fusion 15, December 1975, pp 1031-1043; "Low Power Multiple Shell Fusion Targets for Use With Electron And Ion Beams" by J. D. Lindl et al, International Topical Conference on Electron Beam Research, Albuquerque, New Mexico, Nov. 3-6, 1975 (UCRL-77042); "Stability and Symmetry Requirements of Electron and Ion Beam Fusion Targets" by R. O. Bangerter et al, International E-Beam Conference, Albuquerque, N.M., Nov. 3-6, 1975 (UCRL-77048); and "Fusion Targets Designed to Match Present Relativistic Electron Beam Machine Parameters" by D. J. Meeker et al, The American Physical Society Meeting, Plasma Physics Division, St. Petersburg, Fla., Nov. 10-14, 1975 (UCRL-77045).
The production of fusion neutrons by inertial confinement (implosion) techniques have been experimentally verified, thus verifying the accuracy of computer codes used, as exemplified by "Thermonuclear Fusion Research With High-Power Lasers" by R. R. Johnson et al, Vacuum Technology, May 1975, pp. 56-61 and 64; "Laser Fusion Experiments At The Lawrence Livermore Laboratory" by H. G. Ahlstrom, Gordon Research Conference On Laser Plasma Interaction With Matter, Tilton, N.H., Aug. 18-23, 1975 (UCRL-77094); "Status of Laser Fusion" by J. H. Nuckolls, American Physical Society Meeting, St. Petersburg, Fla., Nov. 10-14, 1975 (UCRL-77056); "Laser Fusion Overview" by J. Nuckolls, Ninth International Quantum Electronics Conference, June 14-18, 1976, Amsterdam, the Netherlands (UCRL-77725); "Electron Beam Fusion Pellets" by W. P. Gula et al, Proceedings of the International Topical Conference on Electron Beam Research and Technology, Nov. 3-6, 1975, Albuquerque, N. Mex. pp. 158-170 (SAND76-5122); and "Behavior of Double Shelled Electron Beam Fusion Targets" by W. P. Gula, Bulletin of the APS, 21, 1195, 1976 (LAUR76-2343).
Target fabrication techniques are at an advanced state of development with numerous mechanisms and processes having been developed, as exemplified by above-referenced U.S. Pat. No. 3,723,246 to M. J. Lubin; as well as U.S. Pat. No. 3,907,477, issued Sept. 23, 1975 to T. R. Jarboe et al; U.S. Pat. No. 3,953,617 issued Apr. 27, 1976 to W. H. Smith et al; U.S. Pat. No. 3,985,841 issued Oct. 12, 1976 to R. J. Turnbull et al; and U.S. Pat. No. 4,012,265 issued Mar. 15, 1977 to J. A. Rinde et al. In addition numerous publications such as paper "Fabrication and Characterization of Laser Fusion Targets" by C. D. Hendricks et al, American Physical Society, Division of Plasma Physics, Nov. 10-14, 1975, St. Petersburg, Fla. (UCRL-76679); and report UCRL-50021-75 "Laser Program Annual Report-1975", Lawrence Livermore Laboratory, Univ. of Cal., Section 7 "Target Fabrication", pp. 343-368, have been prepared in the field of target fabrication.
Thus, while commercial fusion power reactors are still some distance away, the inertial confinement technology has rapidly advanced such that 10.sup.9 fusion neutrons are being produced by existing implosion systems which systems currently provide an excellent source of neutrons, X-rays, alpha particles which has not been previously available to the scientific community for physics studies, radiography, synthetic fuel production, fissile fuel production, tritium production, and radioisotope production, etc. In addition, the energy produced by the implosion of the targets via inertial confinement techniques can be utilized for propulsion applications, process heat production, burning of actinide wastes, etc. Therefore, while fusion power for electrical production has not yet been accomplished, the inertial fusion techniques developed thus far have greatly advanced the state of the art.
With the recognition by the scientific community that inertial fusion has been accomplished, substantial effort is now being directed towards a prototype inertial confinement fusion reactor wherein various systems (laser, e-beam, ion-beam, etc.) are being developed to produce the energy required to implode the targets required for these forthcoming inertial fusion reactor systems. In addition substantial effort is being directed toward development of targets compatible with these energy systems.
In designing ion beam targets suitable for commercial power production, the following criteria are of importance:
1. The target should be cheap; hence, it should be of inexpensive materials, it should be simple to fabricate, and it should be relatively insensitive to fluid instabilities to minimize the precision required in its construction.
2. The target should produce minimum residual radioactivity.
3. The target should have a high gain (energy yield/beam energy) to minimize recirculating power costs in the power plant.
4. The target should have low beam-power and energy requirements.
5. The target should have a large tolerance to irradiation asymmetries.
6. The target should be insensitive to preheat effects.
However, many of the above-listed criteria impose contradictory constraints on target design. For example, power requirements can be lowered by using high-aspect-ratio (radius/shell thickness) shells or multiple-shell designs; but, such targets are relatively unstable and usually have high irradiation symmetry requirements.